While I don't disagree with you in principle, I personally still value outright division titles and would not consider a team with a tie for the best record and the tiebreaker advantage as having won the division title, irrespective of whether that's considered rational anymore.
In any event, as Lee says, I'm an old ****, applying the magic number to an outright league or division title is the way I learned it was done, this is the way I like to do it, and this is how I am going to continue to do it.
In the meantime, enjoy another picture of a Detroit Tiger wearing this morning's magic number.